Answers

No, not if they really are annuals. The term means plants which grow from seed, flower and set seed again in one year. Some plants treated as annuals here are actually perennials - just not in our climate, they don't make it through the winter in the UK where they do in warmer regions. Perennial means it comes up in spring and dies back down in winter, repeating the process the following year and thereafter.

Sorry no, you can,t make them last any longer, seed of annuals are usually sown early in the year, they flower, produce seed and die, then you start again, although some annuals self seed, so they give the impression that they come back every year, Derek.